The present invention relates to a method of producing inner parts of a tripod joint. The inner parts include radial arms followed by a tubular shaft.
It is common practice to produce inner parts of tripod joints by forging or forming the parts with an annular member with inner teeth and subsequent, integrally producing radial arms to receive tripod rollers. An externally toothed tubular shaft is inserted into the inner teeth and axially secured by securing means to the annular member. Furthermore, it is known to form inner parts with an annular member and integral radial arms and to connect the annular member, via an end face, to a tubular shaft by welding. Friction welding is a particularly suitable process for this type of connection. At its end facing away from the tubular shaft, the annular member may be closed by a bottom part. Both above types of forming are described in EP 0 115 232 B1, published Aug. 8, 1984. Machining of the inner parts of both the above described joint designs is relatively complicated since they include three joint arms with deviating axes.
The first mentioned method has a weak point in the region where the arms are connected to the internally toothed annular member. This weak point is due to the joint size and its relatively small wall thickness. In addition, it is relatively expensive to produce the teeth on the tubular shaft and in the annular member.
When selecting material for the inner joint part of the second above mentioned method, a compromise must be made between the wear resistance of the arms and the mechanical load bearing capacity of the inner part, e.g. fracture strength, of the annular member.